Figure 3.

a) Schematic of proposed “on‐demand” reversible deformations of a bilayer derived from a trilayer by switching between exposure to Ca²⁺ and EDTA solutions. b) Cyclic reversible bending of O10M30A/GelMA bilayers due to alternating incubation in EDTA and Ca²⁺ solutions. Inset image shows the reversible bending of the hydrogel bar under alternating stimulations (transparent and red layers are the OMA layer and the GelMA layer, respectively). c) Shape manipulation of a cell‐laden bilayer by alternating Ca²⁺ and EDTA stimulation at 37 °C. d) Photomicrographs of the reversible 3D structure transitions of a quasi‐four‐petal flower by sequential treatment with Ca²⁺ (50 × 10⁻³ m, 10 min) and EDTA (5 × 10⁻³ m, 20 min) solutions. e1) Higher magnification images showing the cells in the GelMA layer and photomicrographs of live/dead stained cells e2) prior to and e3) after Ca²⁺ and EDTA treatment. Photos were taken after replacing the GM with PBS for clarity. Data are presented as mean ± SD, N = 3.